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Abstract

Bimetallic nanoparticles comprised of Iron (Fe) and Nickel (Ni) were investigated for the removal of an azo dye contaminant in water. NiFe nanoparticles were synthesized using a batch aqueous synthesis method that is scalable and environmentally safe. Morphology (core shell and alloy) and metal molar ratio (Ni2Fe10, Ni5Fe10, Ni10Fe10) were tested as key nanoparticle properties. The shelf-life of the nanoparticles was tested over a 3-week period, and the effect of initial nanoparticle concentration on dye removal was evaluated. The highest initial nanoparticle concentration (1000 mg/L) showed consistent Orange G removal and the greatest extent of dye removal, as compared to the other tested concentrations (i.e. 750 mg/L, 500 mg/L, 250 mg/L) for the same nanoparticle morphology and metal molar ratio. The metal molar ratio significantly affected the performance of the core shell morphology, where overall dye removal was found to be 66%, 89%, and 98% with increasing molar ratio (Ni2Fe10 → Ni5Fe10 → Ni10Fe10). In contrast, the overall removal of the dye for all molar ratios of the alloy nanoparticles only resulted in a variability of ± 0.005%. The alloy nanoparticles were able to treat the dye just as effectively after 3 weeks of storage, while the core shell nanoparticles lost reactivity in each successive week. Overall, the Ni2Fe10, Ni5Fe10, and Ni10Fe10 alloy nanoparticles with a starting nanoparticle concentration of 1000 mg/L resulted in the greatest dye removal of 97%, 99%, and 98%, respectively. Kinetic rate models were used to analyze dye removal rate constants as a function of nanoparticle properties, and metal leaching from the nanoparticles was investigated.